There are many orthopedic procedures that involve placing pins or screws into bone. External skeletal fixation involves stabilization of fractured bone segment by pins or screws which protrude through the overlying skin. The pins or screws may be connected to an external frame for stabilization. These external skeletal fixation appliances comprise swivel joints, connecting bars, sliding bars, articulations, and anchorage clamps intended to hold and position transcutaneous pins. For example, when a patient suffers a severe bone injury or undergoes limb-lengthening surgery, it is often necessary to stabilize the fracture area with an external fixation device.
Often, the transcutaneous pins or screws of an external fixation device must remain in place for an extended period. These appliances create a breach in the skin. Because of this breach, the resulting pin-site wound provides a path along which microorganisms present on the skin surface may move into deeper tissues. In addition, inflammation and localized edema at the wound site may lead to a loss of blood flow to the surrounding tissue, decreasing the tissue's ability to fend off infection and slowing the healing process.
The antiseptic effect of vacuum therapy is well-known. Maintaining vacuum pressure on the area around a wound site not only inhibits microbe migration to the wound, it also quickly reduces bacteria population and reproduction in the wound area. Vacuum-assisted wound dressings may comprise a thin film semi-permeable cover containing a perimeter adhesive for creating an air tight seal with the skin. A vacuum tube penetrates the cover. Such dressings are difficult to apply however, where a bone stabilization pin or screw extends through the skin. The vacuum supplied under the cover tends to collapse the thin film cover onto the skin. If used with a protruding pin, the film would tend to tent around the top of pin, and apply an unwanted destabilizing force to the pin.
An alternative vacuum device is disclosed in Argenta et al. (U.S. Pat. No. 5,636,643). Argenta discloses a wound cover that is either rigid or semi-rigid and which has a port for attachment to a vacuum source. The cover fits over the wound and is sealed against the surrounding skin to maintain the vacuum. The device is adapted for use over large open wounds such as burns, pressure sores, and wounds requiring skin grafts or flaps. While a protruding stabilization pin could conceivably be entirely captured within the dome of the rigid cover, the cover is a rather large and unwieldy device and may not be suitable for covering the small wound surrounding a pin. Similarly, such a device would not be suitable for situations in which several pins are used and connected to a common rack or brace, such as in the case of a badly shattered bone. There is also the risk that an external force could cause the pin to rupture the cover.
Yamamoto et al. (U.S. Pat. Nos. 4,856,504 and 4,915,694) disclose antimicrobial wound dressings and skin fixators suitable for use with orthopedic pins and percutaneous conduits (such as catheters), respectively. These devices comprise antimicrobial pads adapted to fit closely to the skin around a pin or conduit. The pad is then covered by a flange with an orthogonally projecting collar which fits around the pin and fits flush with and covers the antimicrobial pad. These devices are aimed at preventing infection around the wound in the patient's skin through use of traditional antiseptic medications and do not contemplate the use of vacuum-assisted healing techniques.
It is therefore apparent that a need exists for a device that can conveniently apply vacuum-assisted treatment to pin-site wounds.